Such a roundsling is for example known from U.S. Pat. Nos. 4,210,089 and 4,850,629. These patent publications disclose roundslings comprising a load-bearing core in the form of parallel turns (also called loops) of load bearing strand material contained within tubular cover means. These roundslings are constructed by forming an endless loop of strands of load-bearing material to form a load-bearing core, e.g. by placing a plurality of turns of said strands in parallel relationship on a surface having guide means mounted on said surface, fastening said turns at their terminal ends to holding means, pulling a tubular cover means having two ends over one of said guide means to envelop said turns, fastening the terminal ends of said parallel load-bearing turns and fastening the terminal ends of said cover means to form an endless loop. In the prior art, the terminal ends of the load-bearing strand material would ordinarily be fastened to another end of a strand of the same material, thus forming an end connection and the entire inner core of load-bearing material would be hidden inside the cover material. Typically, fastening of ends is done by making an end-to-end connection, or by connecting an end to an adjacent turn, e.g. by knotting or with adhesive tape. In case of rounslings that contain a fabric webbing as load-bearing core, the connection can also be made by stitching; as in for example U.S. Pat. No. 4,022,507.
In EP 785 163 A1 a roundsling is described with a load-bearing core containing a filament fibre selected from polyester (e.g. Dacron®), aramid (e.g. Kevlar®), or polyethylene (e.g. Spectra®). A preferred embodiment of EP 785 163 A1 is a roundsling construction comprising a high performance fibre with a tenacity of at least 10 cN/dTex, such as Kevlar® or Spectra® fibre, as a component of the load-bearing core; which construction is light and strong.
A disadvantage of the known roundslings comprising high performance fibers is that their efficiency is rather low. The efficiency of a roundsling here and hereafter is the ratio (in %) of the tenacity of the load-bearing core and the tenacity of the fibre. The efficiency of known roundslings comprising a core of high performance fibres typically is about 20%.
It is the aim of the present invention to provide a roundsling with a higher efficiency then the known slings.
This aim is achieved with a roundsling wherein the strand material is a braided or laid rope, the terminal ends of which are connected with a splice.
With the roundsling of the invention an efficiency of more than 40% can be obtained. The roundsling according to the invention therefore can be made lighter than the known roundslings having the same loading capacity. An extra advantage is the lower volume that can thus be obtained.
In this application a splice is understood to be a tucked or a buried splice, as described in for example The Splicing Handbook, “Techniques for Modern and Traditional Ropes”, by Barbara Merry with John Darwin, ISBN 0-87742-952-9.
In U.S. Pat. No. 4,493,599 buoyant rope assemblies are disclosed that contain a spliced rope. The assemblies described, however, concern a grommet or a hawser but not a roundsling. A grommet is a single endless loop formed by joining two lengths of ropes by end-to-end splices in each leg; a hawser is a single rope with an eye at each end. Nowhere in this publication it is suggested that connecting terminal ends with a splice in a roundsling containing multiple turns of load bearing material would be advantageous.
A roundsling according to European requirements typically comprises 11 turns for one end connection as described in e.g. the standard for polypropylene, polyamide and polyester roundslings EN-1492-2. This relatively high number of turns is required because the end connection in the known roundslings generally is unreliable, thus causing a high variation of the tenacity for slings with less than 11 turns. An advantage of the roundsling of the invention is that the variation of the tenacity is much smaller, even when the number of turns is lower than 11, or even lower than 8. An additional advantage of the roundsling according to the invention is, that also a better efficiency can be obtained when the number of turns is less than 11. Preferably the number of turns is between 2 and 9, or even between 2 and 7.